Sorry I insulted you as that was not my intent.:angel:
I own a chassis/drive train shop and half of my career specializing in RV chassis, so I too know a thing or two about frames under various platforms since I have repaired all kinds. I have no degree except the 1st hand schooling that I have received by seeing what flexes(about to break), breaks, or holds together. No calculator can tell what will/won't break in the field, however it is a great starting point.
More tail sections than not on the Class A and C motor homes are nothing more than a 1 to 8' extension beyond the original frame made up of of 2x4x.120" tube or cheaply formed .180" channel without one single x-member. Then some un-skilled RV production line worker poorly WELDS a class 4 receiver to that. The surrounding body is relied on as the supporting structure!
Take a creeper to the RV dealer. You roll out horrified!
I had a client that hooked up an obviously overloaded 10K GVWR 26' enclosed trailer with the mobile wood shop in it, NO BRAKE CONTROLLER mind you, couldn't understand why 100 psi in the Firestones wasn't enough to level the Class A P32 MH. He was totally unaware that he was driving a time bomb......and he wouldn't believe me!
Again I'm not an engineer and posses no magic paper to hang on my wall, but looking under most larger mid/upper end 5ers I see 10" or better channel or stacked tube,with appropriate x-members front to back. This is much better than what I have been seeing under MH's over the last 18 years.
Note that I didn't recommend the double combo as I have never been under a Big Horn, don't know what the TV is, or what the car is. What if it was a Hummer?! The overall package has to be looked over as a whole and "Engineered" if you will.
I did my own and calcs and determined I was safe. I have no control what anyone else does nor manufactures.
Please accept my apology. However I feel we are both right to an extent and with both sides working to a solution, it could be done safe if the driving skills allowing.
One other thing to consider here....I'm always fixing/improving what some panel engineers said would work.